A number of heart conditions and/or diseases are routinely treated using a pacemaker or implantable cardioverter defibrillator (ICD) that deliver electrical energy to the heart muscle to keep the patient's heart beating at a normal rhythm. Such devices are typically implanted by inserting a thin flexible wire lead into a vein to direct one or more distal electrodes into the atrium and ventricle of the heart. The lead delivers electrical energy to the heart muscle according to a desired rhythm of the heartbeat via the distal electrodes in contact with and/or anchored in the walls of the respective heart chambers. The proximal end of the lead is connected to an energy source that generates the electrical energy provided to the heart via the distal electrode(s).
FIG. 1 illustrates a schematic of one example of a pacemaker implantation. A lead 120 has a terminal connector 130c at one end and distal electrodes 130a and 130b at the other end. The lead is inserted into the right or left subclavian vein and maneuvered such that distal electrode 130a contacts the atrium wall and/or distal electrode 130b contacts the ventricle wall of the heart. The proximal end of the lead (terminal connector) is connected to an energy source that provides electrical energy to the heart, via the lead 120, at a desired rhythm or pattern, which itself undergoes a subcutaneous or submuscular implantation procedure. It should be appreciated that FIG. 1 is not intended to be an accurate depiction of a pacing system, but is merely used to demonstrate the idea of device implantation. For example, the two distal electrodes are illustrated as merging into the same lead, however, multiple electrodes may each have there own independent lead connected to the energy source. Typical pacing systems may include one, two, three, four or more leads and associated electrodes. Moreover, in the dual electrode system shown in FIG. 1, one electrode may be referred to as the distal electrode and the other the proximal electrode (e.g., the tip and ring electrodes used for bipolar stimulation).
Subsequent to implant, lead 120 may need to be extracted from the body for any number of reasons. Infection caused by the pacing system (e.g., infection resulting from the implanted leads or the pacing generator pocket) is the leading reason for a physician to determine that, for the patient's safety, the lead(s) should be extracted from the body. In addition, physical damage to the lead may require lead extraction. For example, fracturing of the lead or damage to the insulation surrounding the lead may cause the device to operate non-optimally, to be altogether non-functional and/or present a risk to the patient, and therefore may require the lead to be extracted and optionally replaced. A lead left in the body from a previously removed device may need to be removed due to interference with a new lead and/or pacing device. For example, an abandoned lead may occupy intravenous space preventing a new lead from being inserted, thus requiring the abandoned lead to be removed.
Lead interaction with the body may also require the lead to be extracted. For example, excessive scar tissue at the tip of the lead may render the lead non-functional and/or may require the device to provide more energy than the device was designed to deliver. Venous obstruction by the lead causing interruption of the blood flow, interference of the lead with the circulatory system or other implanted devices, and/or pain at the site of implant all may recommend extraction of the lead. Numerous other complications may arise that cause a physician to determine that lead extraction is required for the patient's comfort, safety and/or livelihood. For example, a physician may want to replace a lead from a potentially dangerous recalled device or update an older device with a new device to exploit new technological advances.
Many conventional lead extraction devices operate by threading an expandable (“locking”) wire through the lumen of the lead. Standard pacemaker leads are formed from a coiled wire having a hollow center (lumen) along the axis of the lead. The lead lumen may be used to assist in extracting the lead from the body. Such lead extraction devices typically operate by having a guide wire with an outer diameter less than the inner diameter of the lead threaded through the lumen until it reaches the distal end (e.g., the location in which the lead is anchored into the ventricle or atrium wall of the heart).
The guide wire may be provided with a distal portion that can be expanded to engage and grip the internal wire coil of the lead. For example, the distal end of the guide wire may include a coil of wire that can be unwound from the proximal side of the guide wire once the guide wire has reached the distal end (e.g., the implantation end) of the lead. As the wire unwinds, it tangles with the internal wire coil of the lead to anchor the distal end of the guide wire. The guide wire may then be pulled out, extracting the lead along with it.
However, lead extraction may be complicated by tissue adhering to the outer surface of the lead. For example, after the lead has been implanted, scar tissue may form around the lead at any number of different sites (e.g., the insertion point of the lead into the vein or at any location along the vein and/or heart wall) making it difficult for a surgeon to extract the lead without tearing the surrounding tissue. Moreover, if more than one lead is present in the vein, the leads can become attached to one another creating a relatively complicated extraction procedure that is often problematic using conventional lead extraction devices. Lead extraction devices that utilize the internal lumen of the lead for extraction do not address the problem of fibrous tissue attached to the external portion of the lead and may therefore be rendered ineffective, or are used with significant risk of tearing critical internal blood vessels and causing dangerous, and sometimes fatal, damage to the patient should the lead be extracted using excessive force.
To address issues related to tissue adhering to the outside circumference of the lead, conventional methods and devices have used various relatively rudimentary manual devices that cut the surrounding tissue with a knife or edged implement operated by a surgeon and/or utilize laser or diathermic devices that provide laser or electrical energy to cut the surrounding tissue to release the lead for extraction. For example, a hollow sheath having a cutting portion on the distal end may be threaded over the lead. A surgeon may then manually force the sheath forward so that the cutting portion engages the attached tissue and cuts the tissue away from the lead. The surgeon may also manually rotate the sheath to facilitate cutting and or use a trigger gun that attaches to the sheath and that rotates the sheath when the trigger is engaged. In some embodiments, laser or diathermic devices are affixed to the cutting portion of the lead to ablate the tissue to assist in separating surrounding tissue from the lead.